This invention relates generally to methods and apparatus for use in treating proliferative tissue disorders, and more particularly to the treatment of such disorders with a drug eluting brachytherapy device.
Malignant tumors are often treated by surgical resection of the tumor to remove as much of the tumor as possible. Infiltration of the tumor cells into normal tissue surrounding the tumor, however, can limit the therapeutic value of surgical resection because the infiltration can be difficult or impossible to treat surgically. Radiation therapy can be used to supplement surgical resection by targeting the residual tumor margin after resection, with the goal of reducing its size or stabilizing it. Radiation therapy can be administered through one of several methods, or a combination of methods, including external-beam radiation, stereotactic radiosurgery, and permanent or temporary brachytherapy. The term “brachytherapy,” as used herein, refers to radiation therapy delivered by a source of therapeutic rays inserted into the body at or near a tumor or other proliferative tissue disease site. Owing to the proximity of the radiation source, brachytherapy offers the advantage of delivering a more localized dose to the target tissue region.
For example, brachytherapy is performed by implanting radiation sources directly into the tissue to be treated. Brachytherapy is most appropriate where 1) malignant tumor regrowth occurs locally, within 2 or 3 cm of the original boundary of the primary tumor site; 2) radiation therapy is a proven treatment for controlling the growth of the malignant tumor; and 3) there is a radiation dose-response relationship for the malignant tumor, but the dose that can be given safely with conventional external beam radiotherapy is limited by the tolerance of normal tissue. In brachytherapy, radiation doses are highest in close proximity to the radiotherapeutic source, providing a high tumor dose while sparing surrounding normal tissue. Interstitial brachytherapy is useful for treating malignant brain and breast tumors, among others.
Williams U.S. Pat. No. 5,429,582, entitled “Tumor Treatment,” describes a method and apparatus for treating tissue surrounding a surgically excised tumor with radioactive emissions to kill cancer cells that may be present in the tissue surrounding the excised tumor. In addition to the radioactive emissions, Williams discloses external transmitters that can deliver heat to the surrounding tissue, and a permeable balloon through which chemotherapy drugs can seep. Although this device may be effective, permeable materials present some challenges. The permeable materials must be manufactured to precise standards to achieve consistent permeability, and in use, controlling the delivery rate of the chemotherapy drugs can be complicated. Since the delivery rate is dependent on the pressure provided on the chemotherapy drugs, administering the drugs requires extra equipment and attention. In addition, the drugs are delivered uniformly in all directions and cannot be focused on desired regions.